No heat in my coupe.

[91foxbod50]

I just recently purhased a coupe. One problem im having is that I cant get the heat to work. The hoses to the core are connected. But it wont let out heat, and when it does its only for a little while, then after itll get cold.

What ive done,

Changed the t-stat to 180
Flushed out the Heater core with a hose
checked the climate control knob, seems to be on the fritz. know for hot/cold is extremely tight. And the controls for vent floor etc is very touchey.

Any ideas? And no its not leaking at all..

 

[91foxbod50]

anything?

 

[jrichker]

Check the vaccum powered actuators to make sure they are getting vaccum and moving when the control is set to turn them on.
Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.
Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif
Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif
Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg
HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif
TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif
Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

 

[2000xp8]

Follow the vacumm lines jricker is giving you.
Likely you are having a blend door issue.
The power to the blower motor is electrical, but the blend door is controlled by vacuum.

When you turn the knob from vent to defrost or floor, does the air blow out of the right location?

 

[91foxbod50]

yes it does

 

[buddybodean]

This diagram is great, however I am still at a loss. At the top you see the arrow pointing to the "engine compartment vacuum". I traced this into the engine compartment and found the tube disconnected. So, I found out why the HVAC selector stopped working. But, I can't find what this was connected to. Even the service manual doesn't show anything, or I just couldn't find it. Anyone?

 

[Boydster]

This should come very close to helping you find where the line is broken. Maybe make your own drawing to compare...

Note that the Vac res is inside the passenger fender, and the EGR vac regulator, TAB and TAD solenoids are on the back side of the passenger shock tower.

 

[jrichker]

Vacuum is vacuum, connect the line on the check valve to an unused port on the firewall mounted vacuum tree.

 

[buddybodean]

Thanks, but still no help. I am working with a 1995. I found where the HVAC tube runs thru the firewall. I also found the same tube running across the firewall from the drivers side. Behind the drivers side shock tower is a vacuum distribution block where the plastic tube reconnects. I removed all the brittle hard plastic tube and replaced it with 5/32" rubber vacuum line. It easily slips over what was sticking out of the firewall back on the passenger side. I guess I should post pictures. The controls work now and it seems to have helped my idle issues also.